Two-stage grants in unlicensed cells

ABSTRACT

The invention relates to a user equipment (UE) scheduled with uplink radio resources. At least one unlicensed cell is configured for communication between the UE and a base station (BS). The UE receives from the BS a first-stage uplink scheduling message. The UE determines whether the first-stage uplink scheduling message is valid, which comprises determining that it is valid in case one or more bits of one or more data fields in the first-stage uplink scheduling message are set to respectively predetermined values. The UE receives from the BS a second-stage uplink scheduling message related to the first-stage uplink scheduling message. The UE determines, when receiving the second-stage uplink scheduling message, that an uplink transmission is scheduled in case it determined that the first-stage uplink scheduling message is valid. The UE then performs, in case it determined that an uplink transmission is scheduled, an uplink transmission via the unlicensed cell.

BACKGROUND Technical Field

The present disclosure relates to user equipments and radio basestations for scheduling uplink resources in unlicensed cells, as well asto methods for operating radio base stations and the user equipmentsaccordingly.

Description of the Related Art

Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and evolved UMTSTerrestrial Radio Access Network (UTRAN) is finalized as Release 8 (LTERel. 8). The LTE system represents efficient packet-based radio accessand radio access networks that provide full IP-based functionalitieswith low latency and low cost. In LTE, scalable multiple transmissionbandwidths are specified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0MHz, in order to achieve flexible system deployment using a givenspectrum. In the downlink, Orthogonal Frequency Division Multiplexing(OFDM)-based radio access was adopted because of its inherent immunityto multipath interference (MPI) due to a low symbol rate, the use of acyclic prefix (CP) and its affinity to different transmission bandwidtharrangements. Single-carrier frequency division multiple access(SC-FDMA)-based radio access was adopted in the uplink, sinceprovisioning of wide area coverage was prioritized over improvement inthe peak data rate considering the restricted transmit power of the userequipment (UE). Many key packet radio access techniques are employedincluding multiple-input multiple-output (MIMO) channel transmissiontechniques and a highly efficient control signaling structure isachieved in LTE Rel. 8/9.

LTE Architecture

The overall LTE architecture is shown in FIG. 1. The E-UTRAN consists ofan eNodeB, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) andcontrol plane (RRC) protocol terminations towards the user equipment(UE). The eNodeB (eNB) hosts the Physical (PHY), Medium Access Control(MAC), Radio Link Control (RLC) and Packet Data Control Protocol (PDCP)layers that include the functionality of user-plane header compressionand encryption. It also offers Radio Resource Control (RRC)functionality corresponding to the control plane. It performs manyfunctions including radio resource management, admission control,scheduling, enforcement of negotiated uplink Quality of Service (QoS),cell information broadcast, ciphering/deciphering of user and controlplane data, and compression/decompression of downlink/uplink user planepacket headers. The eNodeBs are interconnected with each other by meansof the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle-state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, or network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle-mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at the time ofintra-LTE handover involving Core Network (CN) node relocation. It isresponsible for authenticating the user (by interacting with the HSS).The Non-Access Stratum (NAS) signaling terminates at the MME, and it isalso responsible for the generation and allocation of temporaryidentities to user equipments. It checks the authorization of the userequipment to camp on the service provider's Public Land Mobile Network(PLMN) and enforces user equipment roaming restrictions. The MME is thetermination point in the network for ciphering/integrity protection forNAS signaling and handles the security key management. Lawfulinterception of signaling is also supported by the MME. The MME alsoprovides the control plane function for mobility between LTE and 2G/3Gaccess networks with the S3 interface terminating at the MME from theSGSN. The MME also terminates the S6a interface towards the home HSS forroaming user equipments.

Component Carrier Structure in LTE

The downlink component carrier of a 3GPP LTE system is subdivided in thetime-frequency domain in so-called subframes. In 3GPP LTE each subframeis divided into two downlink slots as shown in FIG. 2, wherein the firstdownlink slot comprises the control channel region (PDCCH region) withinthe first OFDM symbols. Each subframe consists of a give number of OFDMsymbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release8)), wherein each OFDM symbol spans over the entire bandwidth of thecomponent carrier. The OFDM symbols thus each consist of a number ofmodulation symbols transmitted on respective subcarriers. In LTE, thetransmitted signal in each slot is described by a resource grid ofN_(RB) ^(DL)N_(sc) ^(RB) subcarriers and N_(symb) ^(DL) OFDM symbols.N_(RB) ^(DL) is the number of resource blocks within the bandwidth. Thequantity N_(RB) ^(DL) depends on the downlink transmission bandwidthconfigured in the cell and shall fulfill N_(RB) ^(min,DL)≤N_(RB)^(DL)≤N_(RB) ^(max,DL), where N_(RB) ^(min,DL)=6 and N_(RB)^(max,DL)=110 are respectively the smallest and the largest downlinkbandwidths, supported by the current version of the specification.N_(sc) ^(RB) is the number of subcarriers within one resource block. Fornormal cyclic prefix subframe structure, N_(sc) ^(RB)=12 and N_(symb)^(DL)=7.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block (PRB) is defined as consecutive OFDM symbolsin the time domain (e.g., 7 OFDM symbols) and consecutive subcarriers inthe frequency domain as exemplified in FIG. 2 (e.g., 12 subcarriers fora component carrier). In 3GPP LTE (Release 8), a physical resource blockthus consists of resource elements, corresponding to one slot in thetime domain and 180 kHz in the frequency domain (for further details onthe downlink resource grid, see for example 3GPP TS 36.211, “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation (Release 8)”, current version 12.6.0, section 6.2, availableat http://www.3gpp.org and incorporated herein by reference).

One subframe consists of two slots, so that there are 14 OFDM symbols ina subframe when a so-called “normal” CP (cyclic prefix) is used, and 12OFDM symbols in a subframe when a so-called “extended” CP is used. Forsake of terminology, in the following the time-frequency resourcesequivalent to the same consecutive subcarriers spanning a full subframeis called a “resource block pair”, or equivalent “RB pair” or “PRBpair”. The term “component carrier” refers to a combination of severalresource blocks in the frequency domain. In future releases of LTE, theterm “component carrier” is no longer used; instead, the terminology ischanged to “cell”, which refers to a combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources.

Similar assumptions for the component carrier structure will apply tolater releases too.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

The frequency spectrum for IMT-Advanced was decided at the World Radiocommunication Conference 2007 (WRC-07). Although the overall frequencyspectrum for IMT-Advanced was decided, the actual available frequencybandwidth is different according to each region or country. Followingthe decision on the available frequency spectrum outline, however,standardization of a radio interface started in the 3rd

Generation Partnership Project (3GPP).

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality.

In carrier aggregation, two or more component carriers are aggregated inorder to support wider transmission bandwidths up to 100 MHz. Severalcells in the LTE system are aggregated into one wider channel in theLTE-Advanced system which is wide enough for 100 MHz even though thesecells in LTE may be in different frequency bands. All component carrierscan be configured to be LTE Rel. 8/9 compatible, at least when thebandwidth of a component carrier does not exceed the supported bandwidthof an LTE Rel. 8/9 cell. Not all component carriers aggregated by a userequipment may necessarily be Rel. 8/9 compatible. Existing mechanisms(e.g., barring) may be used to avoid Rel-8/9 user equipments to camp ona component carrier.

A user equipment may simultaneously receive or transmit on one ormultiple component carriers (corresponding to multiple serving cells)depending on its capabilities. An LTE-A Rel. 10 user equipment withreception and/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain (using the 3GPP LTE (Release8/9) numerology).

It is possible to configure a 3GPP LTE-A (Release 10)-compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. The number ofdownlink component carriers that can be configured depends on thedownlink aggregation capability of the UE. Conversely, the number ofuplink component carriers that can be configured depends on the uplinkaggregation capability of the UE. It may currently not be possible toconfigure a mobile terminal with more uplink component carriers thandownlink component carriers. In a typical TDD deployment the number ofcomponent carriers and the bandwidth of each component carrier in uplinkand downlink is the same. Component carriers originating from the sameeNodeB need not provide the same coverage.

The spacing between center frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time to preserve orthogonality of the subcarrierswith 15 kHz spacing. Depending on the aggregation scenario, the n×300kHz spacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmission(s) needto be mapped on the same component carrier.

When carrier aggregation is configured, the mobile terminal only has oneRRC connection with the network. At RRC connectionestablishment/re-establishment, one cell provides the security input(one ECGI, one PCI and one ARFCN) and the non-access stratum mobilityinformation (e.g., TAI) similarly as in LTE Rel. 8/9. After RRCconnection establishment/re-establishment, the component carriercorresponding to that cell is referred to as the downlink Primary Cell(PCell). There is always one and only one downlink PCell (DL PCell) andone uplink PCell (UL PCell) configured per user equipment in connectedstate. Within the configured set of component carriers, other cells arereferred to as Secondary Cells (SCells); with carriers of the SCellbeing the Downlink Secondary Component Carrier (DL SCC) and UplinkSecondary Component Carrier (UL SCC). Maximum five serving cells,including the PCell, can be configured at the moment for one UE.

The configuration and reconfiguration, as well as addition and removal,of component carriers can be performed by RRC. Activation anddeactivation is done e.g., via MAC control elements. At intra-LTEhandover, RRC can also add, remove, or reconfigure SCells for usage inthe target cell. When adding a new SCell, dedicated RRC signaling isused for sending the system information of the SCell, the informationbeing necessary for transmission/reception (similarly as in Rel-8/9 forhandover). Each SCell is configured with a serving cell index, when theSCell is added to one UE; PCell has always the serving cell index 0.

When a user equipment is configured with carrier aggregation there is atleast one pair of uplink and downlink component carriers that is alwaysactive. The downlink component carrier of that pair might be alsoreferred to as ‘DL anchor carrier’. Same applies also for the uplink.When carrier aggregation is configured, a user equipment may bescheduled on multiple component carriers simultaneously, but at most onerandom access procedure shall be ongoing at any time. Cross-carrierscheduling allows the PDCCH of a component carrier to schedule resourceson another component carrier. For this purpose a component carrieridentification field is introduced in the respective DCI (DownlinkControl Information) formats, called CIF.

A linking, established by RRC signaling, between uplink and downlinkcomponent carriers allows identifying the uplink component carrier forwhich the grant applies when there is no cross-carrier scheduling. Thelinkage of downlink component carriers to uplink component carrier doesnot necessarily need to be one to one. In other words, more than onedownlink component carrier can link to the same uplink componentcarrier. At the same time, a downlink component carrier can only link toone uplink component carrier.

Uplink/Downlink Scheduling

A MAC function in the eNodeB refers to scheduling, by which the eNBdistributes the available radio resources in one cell among the UEs andamong the radio bearers for each UE. In principle, the eNodeB allocatesthe downlink and uplink resources to each UE based on respectively thedownlink data buffered in the eNodeB and based on buffer status reports(BSRs) received from the UE. In this process, the eNodeB considers theQoS requirements of each configured radio bearer and selects the size ofthe MAC PDU.

The usual mode of scheduling is dynamic scheduling, by means of downlinkgrant/assignment messages (DCIs) for the allocation of downlinktransmission resources and uplink grant/assignment messages for theallocation of uplink transmission resources. They are transmitted on thephysical downlink control channel (PDCCH) using a cell radio networktemporary identifier (C-RNTI) to identify the intended UE. In additionto the dynamic scheduling, persistent scheduling is defined, whichenables radio resources to be semi-statically configured and allocatedto a UE for a longer time period than one subframe, thus avoiding theneed for specific downlink assignment messages or uplink grant messagesover the PDCCH for each subframe. For the configuration orreconfiguration of a persistent schedule, RRC signaling indicates theresource allocation interval at which the radio resources areperiodically assigned. When the PDCCH is used to configure orreconfigure a persistent schedule, it is necessary to distinguish thescheduling messages which apply to a persistent schedule from those usedfor dynamic scheduling. For this purpose, a special scheduling identityis used, known as the semi-persistent scheduling C-RNTI, SPS-C-RNTI,which for each UE is different from the C-RNTI used for dynamicscheduling messages.

In order to inform the scheduled users about their allocation status,transport format and other transmission-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length can be amultiple of the subframes. The TTI length may be fixed in a service areafor all users, may be different for different users, or may even bydynamic for each user. Generally, the L1/2 control signaling needs onlybe transmitted once per TTI. Without loss of generality, the followingassumes that a TTI is equivalent to one subframe.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which in most cases includes resource assignments andother control information for a mobile terminal or groups of UEs. Ingeneral, several PDCCHs can be transmitted in one subframe.

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in their fields. Thedifferent DCI formats that are currently defined for LTE are describedin detail in 3GPP TS 36.212, “Multiplexing and channel coding”, section5.3.3.1 (current version v12.6.0 available at http://www.3gpp.org andincorporated herein by reference). For detailed information regardingthe DCI formats and the particular information that is transmitted inthe DCI, please refer to the mentioned technical standard or to LTE—TheUMTS Long Term Evolution—From Theory to Practice, Edited by StefanieSesia, Issam Toufik, Matthew Baker, Chapter 9.3, incorporated herein byreference. Additional formats may be defined in the future.

Layer 1/Layer 2 Control Signaling

In order to inform the scheduled users about their allocation status,transport format, and other transmission-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length can be amultiple of the subframes. The TTI length may be fixed in a service areafor all users, may be different for different users, or may even bydynamic for each user. Generally, the L1/2 control signaling needs onlybe transmitted once per TTI. Without loss of generality, the followingassumes that a TTI is equivalent to one subframe.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which in most cases includes resource assignments andother control information for a mobile terminal or groups of UEs. Ingeneral, several PDCCHs can be transmitted in one subframe.

It should be noted that in 3GPP LTE, assignments for uplink datatransmissions, also referred to as uplink scheduling grants or uplinkresource assignments, are also transmitted on the PDCCH. Furthermore,3GPP Release 11 introduced an EPDCCH that fulfills basically the samefunction as the PDCCH, i.e., conveys L1/L2 control signaling, eventhough the detailed transmission methods are different from the PDCCH.Further details can be found in the current versions of 3GPP TS 36.211and 36.213, incorporated herein by reference. Consequently, most itemsoutlined in the background and the embodiments apply to PDCCH as well asEPDCCH, or other means of conveying L1/L2 control signals, unlessspecifically noted.

Generally, the information sent in the L1/L2 control signaling forassigning uplink or downlink radio resources (particularly LTE(-A)Release 10) can be categorized to the following items:

-   -   User identity, indicating the user that is allocated. This is        typically included in the checksum by masking the CRC with the        user identity;    -   Resource allocation information, indicating the resources (e.g.,        Resource Blocks, RBs) on which a user is allocated.        Alternatively this information is termed resource block        assignment (RBA). Note, that the number of RBs on which a user        is allocated can be dynamic;    -   Carrier indicator, which is used if a control channel        transmitted on a first carrier assigns resources that concern a        second carrier, i.e., resources on a second carrier or resources        related to a second carrier; (cross carrier scheduling);    -   Modulation and coding scheme that determines the employed        modulation scheme and coding rate;    -   HARQ information, such as a new data indicator (NDI) and/or a        redundancy version (RV) that is particularly useful in        retransmissions of data packets or parts thereof;    -   Power control commands to adjust the transmit power of the        assigned uplink data or control information transmission;    -   Reference signal information such as the applied cyclic shift        and/or orthogonal cover code index, which are to be employed for        transmission or reception of reference signals related to the        assignment;    -   Uplink or downlink assignment index that is used to identify an        order of assignments, which is particularly useful in TDD        systems;    -   Hopping information, e.g., an indication whether and how to        apply resource hopping in order to increase the frequency        diversity;    -   CSI request, which is used to trigger the transmission of        channel state information in an assigned resource; and    -   Multi-cluster information, which is a flag used to indicate and        control whether the transmission occurs in a single cluster        (contiguous set of RBs) or in multiple clusters (at least two        non-contiguous sets of contiguous RBs). Multi-cluster allocation        has been introduced by 3GPP LTE-(A) Release 10.

It is to be noted that the above listing is non-exhaustive, and not allmentioned information items need to be present in each PDCCHtransmission depending on the DCI format that is used.

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in their fields asmentioned above. In the following, some DCI formats are listed ascurrently defined for LTE. More detailed information is provided in the3GPP technical standard TS 36.212 v14.0.0, particularly in section5.3.3.1 “DCI formats”, incorporated herein by reference.

-   -   Format 0: DCI Format 0 is used for the transmission of resource        grants for the PUSCH, using single-antenna port transmissions in        uplink transmission mode 1 or 2.    -   Format 1: DCI Format 1 is used for the transmission of resource        assignments for single codeword PDSCH transmissions (downlink        transmission modes 1, 2 and 7).    -   Format 1A: DCI Format 1A is used for compact signaling of        resource assignments for single codeword PDSCH transmissions,        and for allocating a dedicated preamble signature to a mobile        terminal for contention-free random access (for all        transmissions modes).    -   Format 1B: DCI Format 1B is used for compact signaling of        resource assignments for PDSCH transmissions using closed loop        precoding with rank-1 transmission (downlink transmission mode        6). The information transmitted is the same as in Format 1A, but        with the addition of an indicator of the precoding vector        applied for the PDSCH transmission.    -   Format 1C: DCI Format 1C is used for very compact transmission        of PDSCH assignments. When format 1C is used, the PDSCH        transmission is constrained to using QPSK modulation. This is        used, for example, for signaling paging messages and broadcast        system information messages.    -   Format 1D: DCI Format 1D is used for compact signaling of        resource assignments for PDSCH transmission using multi-user        MIMO. The information transmitted is the same as in Format 1B,        but instead of one of the bits of the precoding vector        indicators, there is a single bit to indicate whether a power        offset is applied to the data symbols. This feature is needed to        show whether or not the transmission power is shared between two        UEs. Future versions of LTE may extend this to the case of power        sharing between larger numbers of UEs.    -   Format 2: DCI Format 2 is used for the transmission of resource        assignments for PDSCH for closed-loop MIMO operation        (transmission mode 4).    -   Format 2A: DCI Format 2A is used for the transmission of        resource assignments for PDSCH for open-loop MIMO operation. The        information transmitted is the same as for Format 2, except that        if the eNodeB has two transmit antenna ports, there is no        precoding information, and for four antenna ports two bits are        used to indicate the transmission rank (transmission mode 3).    -   Format 2B: Introduced in Release 9 and is used for the        transmission of resource assignments for PDSCH for dual-layer        beamforming (transmission mode 8).    -   Format 2C: Introduced in Release 10 and is used for the        transmission of resource assignments for PDSCH for closed-loop        single-user or multi-user MIMO operation with up to 8 layers        (transmission mode 9).    -   Format 2D: introduced in Release 11 and used for up to 8 layer        transmissions; mainly used for COMP (Cooperative Multipoint)        (transmission mode 10)    -   Format 3 and 3A: DCI formats 3 and 3A are used for the        transmission of power control commands for PUCCH and PUSCH with        2-bit or 1-bit power adjustments respectively. These DCI formats        contain individual power control commands for a group of UEs.    -   Format 4: DCI format 4 is used for the scheduling of the PUSCH,        using closed-loop spatial multiplexing transmissions in uplink        transmission mode 2.    -   Format 5: DCI format 5 is used for the scheduling of the PSCCH        (Physical Sidelink Control Channel), and also contains several        SCI format 0 fields used for the scheduling of the PSSCH        (Physical Sidelink Shared Control Channel). If the number of        information bits in DCI format 5 mapped onto a given search        space is less than the payload size of format 0 for scheduling        the same serving cell, zeros shall be appended to format 5 until        the payload size equals that of format 0 including any padding        bits appended to format 0.        LTE on Unlicensed Bands—Licensed-Assisted Access (LAA)

In September 2014, 3GPP initiated a new study item on LTE operation onunlicensed spectrum. The reason for extending LTE to unlicensed bands isthe ever-growing demand for wireless broadband data in conjunction withthe limited amount of licensed bands. The unlicensed spectrum thereforeis more and more considered by cellular operators as a complementarytool to augment their service offering. One advantage of LTE inunlicensed bands compared to relying on other radio access technologies(RAT) such as Wi-Fi is that complementing the LTE platform withunlicensed spectrum access enables operators and vendors to leverage theexisting or planned investments in LTE/EPC hardware in the radio andcore network.

However, it has to be taken into account that unlicensed spectrum accesscan never match the qualities of licensed spectrum access due to theinevitable coexistence with other radio access technologies (RATs) inthe unlicensed spectrum such as Wi-Fi. LTE operation on unlicensed bandswill therefore at least in the beginning be considered a complement toLTE on licensed spectrum rather than as stand-alone operation onunlicensed spectrum. Based on this assumption, 3GPP established the termLicensed Assisted Access (LAA) for the LTE operation on unlicensed bandsin conjunction with at least one licensed band. Future stand-aloneoperation of LTE on unlicensed spectrum i.e., without being assisted bylicensed cells, however shall not be excluded. Enhanced LicensedAssisted Access (eLAA) is enhancement to LAA, particularly exploitingthe unlicensed spectrum in the uplink as well. Efficient use ofunlicensed spectrum as a complement to licensed spectrum has thepotential to bring great value to service providers, and, ultimately, tothe wireless industry as a whole. To leverage the full benefits of LTEoperation in unlicensed spectrum, it is of outmost importance to definea complete UL access scheme in addition to the already defined DL accessscheme.

The currently-intended general LAA approach at 3GPP is to make use ofthe already specified Rel-12 carrier aggregation (CA) framework as muchas possible, where the CA framework configuration as explained beforecomprises a so-called primary cell (PCell) carrier and one or moresecondary cell (SCell) carriers. CA supports in general bothself-scheduling of cells (scheduling information and user data aretransmitted on the same component carrier) and cross-carrier schedulingbetween cells (scheduling information in terms of PDCCH/EPDCCH and userdata in terms of PDSCH/PUSCH are transmitted on different componentcarriers).

A very basic scenario is illustrated in FIG. 4, with a licensed PCell,licensed SCell 1, and various unlicensed SCells 2, 3, and 4 (exemplarilydepicted as small cells). The transmission/reception network nodes ofunlicensed SCells 2, 3, and 4 could be remote radio heads managed by theeNB or could be nodes that are attached to the network but not managedby the eNB. For simplicity, the connection of these nodes to the eNB orto the network is not explicitly shown in the figure.

At present, the basic approach envisioned at 3GPP is that the PCell willbe operated on a licensed band while one or more SCells will be operatedon unlicensed bands. One benefit of this strategy is that the PCell canbe used for reliable transmission of control messages and user data withhigh quality of service (QoS) demands, such as for example voice andvideo, while an SCell on unlicensed spectrum might yield, depending onthe scenario, to some extent significant QoS reduction due to inevitablecoexistence with other RATs.

It has been agreed that the LAA will focus on unlicensed bands at 5 GHz.One of the most critical issues is therefore the coexistence with Wi-Fi(IEEE 802.11) systems operating at these unlicensed bands. In order tosupport fair coexistence between LTE and other technologies such asWi-Fi as well as to guarantee fairness between different LTE operatorsin the same unlicensed band, the channel access of LTE for unlicensedbands has to abide by certain sets of regulatory rules which may partlydepend on the geographical region and particular frequency band; acomprehensive description of the regulatory requirements for all regionsfor operation on unlicensed bands at 5 GHz is given in R1-144348,“Regulatory Requirements for Unlicensed Spectrum”, Alcatel-Lucent etal., RAN1#78bis, September 2014 incorporated herein by reference as wellas the 3GPP Technical Report 36.889, current version 13.0.0. Dependingon region and band, regulatory requirements that have to be taken intoaccount when designing LAA procedures comprise Dynamic FrequencySelection (DFS), Transmit Power Control (TPC), Listen Before Talk (LBT)and discontinuous transmission with limited maximum transmissionduration. The intention of 3GPP is to target a single global frameworkfor LAA which basically means that all requirements for differentregions and bands at 5 GHz have to be taken into account for the systemdesign.

For example, in Europe certain limits for the Nominal Channel Bandwidthis set, as apparent from section 4.3 of the European standard ETSI EN301 893, current version 1.8.1, incorporated herein by reference. TheNominal Channel Bandwidth is the widest band of frequencies, inclusiveof guard bands, assigned to a single channel. The Occupied ChannelBandwidth is the bandwidth containing 99% of the power of the signal. Adevice is permitted to operate in one or more adjacent or non-adjacentchannels simultaneously.

The listen-before-talk (LBT) procedure is defined as a mechanism bywhich an equipment applies a clear channel assessment (CCA) check beforeusing the channel. The CCA utilizes at least energy detection todetermine the presence or absence of other signals on a channel in orderto determine if a channel is occupied or clear, respectively. Europeanand Japanese regulations at the moment mandate the usage of LBT in theunlicensed bands. Apart from regulatory requirements, carrier sensingvia LBT is one way for fair sharing of the unlicensed spectrum and henceit is considered to be a vital feature for fair and friendly operationin the unlicensed spectrum in a single global solution framework.

In unlicensed spectrum, channel availability cannot always beguaranteed. In addition, certain regions such as Europe and Japanprohibit continuous transmissions and impose limits on the maximumduration of a transmission burst in the unlicensed spectrum. Hence,discontinuous transmission with limited maximum transmission duration isa required functionality for LAA. DFS is required for certain regionsand bands in order to detect interference from radar systems and toavoid co-channel operation with these systems. The intention isfurthermore to achieve a near-uniform loading of the spectrum. The DFSoperation and corresponding requirements are associated with amaster-slave principle. The master shall detect radar interference, canhowever rely on another device, associated with the master, to implementradar detection.

The operation on unlicensed bands at 5-GHz is in most regions limited torather low transmit power levels compared to the operation on licensedbands which results in small coverage areas. Even if the licensed andunlicensed carriers were to be transmitted with identical power, usuallythe unlicensed carrier in the 5 GHz band would be expected to support asmaller coverage area than a licensed cell in the 2 GHz band due toincreased path loss and shadowing effects for the signal. A furtherrequirement for certain regions and bands is the use of TPC in order toreduce the average level of interference caused for other devicesoperating on the same unlicensed band.

Detailed information can be found in the harmonized European standardETSI EN 301 893, current version 1.8.1, incorporated herein byreference.

Following this European regulation regarding LBT, devices have toperform a clear channel Assessment (CCA) before occupying the radiochannel with a data transmission. It is only allowed to initiate atransmission on the unlicensed channel after detecting the channel asfree based e.g., on energy detection. In particular, the equipment hasto observe the channel for a certain minimum time (e.g., for Europe 20μs, see ETSI 301 893, under clause 4.8.3) during the CCA. The channel isconsidered occupied if the detected energy level exceeds a configuredCCA threshold (e.g., for Europe, −73 dBm/MHz, see ETSI 301 893, underclause 4.8.3), and conversely is considered to be free if the detectedpower level is below the configured CCA threshold. If the channel isdetermined as being occupied, it shall not transmit on that channelduring the next Fixed Frame Period. If the channel is classified asfree, the equipment is allowed to transmit immediately. The maximumtransmit duration is restricted in order to facilitate fair resourcesharing with other devices operating on the same band.

The energy detection for the CCA is performed over the whole channelbandwidth (e.g., 20 MHz in unlicensed bands at 5 GHz), which means thatthe reception power levels of all subcarriers of an LTE OFDM symbolwithin that channel contribute to the evaluated energy level at thedevice that performed the CCA.

In addition to the CCA described above, it might be required to apply anadditional extended CCA (ECCA) if the equipment is classified as LoadBased Equipment (LBE) according to the description in ETSI 301 893,clause 4.9.2.2, incorporated herein by reference. The ECCA comprises anadditional CCA observation time for the duration of a random factor Nmultiplied by a CCA observation time slot. N defines the number of clearidle slots resulting in a total idle period that has to be observedbefore initiating a transmission.

Furthermore, the total time during which an equipment has transmissionson a given carrier without re-evaluating the availability of thatcarrier (i.e., LBT/CCA) is defined as the Channel Occupancy Time (seeETSI 301 893, under clause 4.8.3.1). The Channel Occupancy Time shall bein the range of 1 ms to 10 ms, where the maximum Channel Occupancy Timecould be e.g., 4 ms as currently defined for Europe. Furthermore, thereis a minimum Idle time the UE is not allowed to transmit after atransmission on the unlicensed cell, the minimum Idle time being atleast 5% of the Channel Occupancy Time. Towards the end of the IdlePeriod, the UE can perform a new CCA, and so on. This transmissionbehavior is schematically illustrated in FIG. 5, the figure being takenfrom ETSI EN 301 893 (there FIG. 2: “Example of timing for Frame BasedEquipment”).

FIG. 6 illustrates the timing between a Wi-Fi transmission and LAA UEtransmissions on a particular frequency band (unlicensed cell). As canbe seen from FIG. 5, after the Wi-Fi burst, a CCA gap is at leastnecessary before the eNB “reserves” the unlicensed cell by e.g.,transmitting a reservation signal until the next subframe boundary.Then, the actual LAA DL burst is started. This would similarly apply toan LTE UE which after successfully performing the CCA, would reserve thesubframe by transmitting the reservation signal so as to then start theactual LAA UL burst.

Uplink Scheduling in Unlicensed Cells

DCI Formats 0A, 0B, 4A, and 4B are provided for eLAA so as to supportuplink transmissions (PUSCH) for single subframe and multiple subframegrants and respectively single and multiple antenna ports.

-   -   DCI Format 0A: Single subframe, single antenna port    -   DCI Format 0B: Multiple subframe, single antenna port    -   DCI Format 4A: Single subframe, multiple antenna ports    -   DCI Format 4B: Multiple subframe, multiple antenna ports

Details on these DCI format can be found in 3GPP technical standard TS36.212 v14.0.0, sections 5.3.3.1.1A, 5.3.3.1.1B, 5.3.3.1.8A, 5.3.3.1.8B,incorporated herein by reference.

Any of these DCI formats (i.e., Uplink grants) can be either asingle-stage grant or be part of a two-stage grant. In the currentexemplary implementations in LTE (see TS 36.212), this is reflected bythe “PUSCH trigger A”-field, which is a 1-bit field differentiatingwhether the received Uplink grant is for “a non-triggered scheduling”,when the bit value is 0 (i.e., single-stage uplink grant) or is for“triggered scheduling”, when the bit value is 1 (i.e., two-stage uplinkgrant). This can be controlled by the eNB, which is the responsibleradio network entity for the scheduling of radio resources to the UE.

The two-stage uplink scheduling procedure requires two separate messages(“Trigger A” and “Trigger B”) to be received in a specific manner by theUE so as to schedule one uplink transmission.

The trigger-A-message can be any of the above-noted uplink grants (i.e.,DCI Formats 0A, 0B, 4A, or 4B). In connection with this two-stage grant,the four DCI Formats include the following data fields, as presentlydefined in the technical standard TS 36.212 v14.0.0:

“PUSCH trigger A—1 bit, where value 0 indicates non-triggered schedulingand value 1 indicates triggered scheduling as defined in section 8.0 of[3].

-   -   Timing offset—4 bits as defined in [3]        -   When the flag for triggered scheduling is set to 0,            -   The field indicates the absolute timing offset for the                PUSCH transmission.        -   Otherwise,            -   The first two bits of the field indicate the relative                timing offset for the PUSCH transmission.            -   The last two bits of the field indicate the time window                within which the scheduling of PUSCH via triggered                scheduling is valid”

In addition, the available DCI Formats for the trigger-A message alsoinclude the usual data fields for indicating the radio resources thatare scheduled for an uplink transmission, such as the “Resource blockassignment” field, the “modulation and coding scheme” field, “HARQprocess number” field etc. Moreover, the DCI formats 0A, 0B, 4A, 4B(particularly the DCI CRC) can be scrambled with a UE specific identity(such as the C-RNTI), such that the corresponding uplink grants areaddressed to a specific UE.

The trigger-B-message has the DCI Format 1C as currently defined in TS36.212 v14.0.0, section 5.3.3.1.4, incorporated herein by reference. TheDCI Format 1C, as currently defined in the technical standard for usewithin the scope of unlicensed carrier transmissions, including atwo-stage grant procedure, is as follows:

“Else

-   -   Subframe configuration for LAA—4 bits as defined in section 13A        of [3]    -   Uplink transmission duration and offset indication—5 bits as        defined in section 13A of [3]. The field only applies to a UE        configured with uplink transmission on a LAA SCell    -   PUSCH trigger B—1 bit as defined in section 8.0 of [3]. The        field only applies to a UE configured with uplink transmission        on a LAA SCell    -   Reserved information bits are added until the size is equal to        that of format 1C used for very compact scheduling of one PDSCH        codeword”

The trigger B message (DCI Format 1C), when being used as describedabove as part of the two-stage grant procedure, is usually not addressedto a specific UE but rather a shared identity (in this case the CC-RNTI;Common Control RNTI, which is an RNTI to be used in the context ofproviding common control PDCCH information; see 3GPP TS 36.321 v14.0.0,incorporated herein by reference) can be used by the eNB to scramble theDCI Format 1C, particularly the CRC thereof.

The cross-reference “[3]” in the above citations of TS 36.212 refers tothe technical standard 3GPP TS 36.213, current version 14.0.0, of whichat least sections 8.0 and 13 are relevant to the two-stage grants andare thus incorporated herein by reference in their entirety.

Particularly, section 8 of TS 36.213 defines in great detail for an LAASCell when and how an uplink transmission (i.e., PUSCH) is to beperformed:

“For a serving cell that is a LAA SCell, a UE shall

-   -   upon detection of an PDCCH/EPDCCH with DCI format 0A/0B/4A/4B        and with ‘PUSCH trigger A’ field set to ‘0’ in subframe n        intended for the UE, or    -   upon detection of PDCCH/EPDCCH with DCI format 0A/0B/4A/4B and        with ‘PUSCH trigger A’ field set to ‘1’ in the most recent        subframe from subframe n-v intended for the UE, and upon        detection of PDCCH with DCI CRC scrambled by CC-RNTI and with        ‘PUSCH trigger B’ field set to ‘1’ in subframe n

perform a corresponding PUSCH transmission, conditioned on the channelaccess procedures described in clause 15.2.1, in subframe(s) n+l+k+iwith i=0, 1, . . . , N−1 according to the PDCCH/EPDCCH and HARQ processID mod (n_(HARQ_ID)+i,N_(HARQ))

where

-   -   N=1 for DCI format 0A/4A, and value of N is determined by the        ‘number of scheduled subframes’ field in the corresponding DCI        format 0B/4B.        -   The UE is configured the maximum value of N by higher layer            parameter maxNumberOfSchedSubframes-FormatOB for DCI format            0B and higher layer parameter            maxNumberOfSchedSubframes-Format4B for DCI format 4B;    -   value of k is determined by the scheduling delay field in the        corresponding DCI 0A/0B/4A/4B according to Table 8.2d if ‘PUSCH        trigger A’ field set to ‘0’ or Table 8.2e otherwise;    -   value of n_(HARQ_ID) is determined by the HARQ process number        field in the corresponding DCI format 0A/0B/4A/4B and        N_(HARQ)=16;    -   for ‘PUSCH trigger A’ field set to ‘0’ in the corresponding DCI        format 0A/0B/4A/4B,        -   1=4    -   otherwise        -   value of 1 is the UL offset as determined by the ‘UL            configuration for LAA’ field in the corresponding DCI with            CRC scrambled by CC-RNTI according to the procedure in            subclause 13A, and ‘PUSCH trigger B’ field set to ‘1’,        -   value of v is determined by the validation duration field in            the corresponding PDCCH/EPDCCH with DCI format 0A/0B/4A/4B            according to Table 8.2f, and ‘PUSCH trigger A’ field set to            ‘1’        -   the smallest value of l+k supported by the UE is included in            the UE-EUTRA-Capability

TABLE 8.2d k for DCI format 0A/0B/4A/4B with ‘PUSCH trigger A’ field setto ‘0’. Value of ‘scheduling delay’ field k 0000 0 0001 1 0010 2 0011 30100 4 0101 5 0110 6 0111 7 1000 8 1001 9 1010 10 1011 11 1100 12 110113 1110 14 1111 15

TABLE 8.2e k for DCI format 0A/0B/4A/4B with ‘PUSCH trigger A’ field setto ‘1’. Value of ‘scheduling delay’ field k 00 0 01 1 10 2 11 3

TABLE 8.2f v for DCI format 0A/0B/4A/4B with ‘PUSCH trigger A’ field setto ‘1’. Value of ‘validation duration’ field v 00 8 01 12 10 16 11 20

The current 3GPP technical standards thus define in great detail how atwo-stage grant procedure is to be performed. It should be however notedthat the above provided definition of two-stage grant procedures ascurrently standardized is subject to a continuous change and improvementand thus may change in the future. Consequently, the above citedimplementation of the two-stage grant procedure according to the current3GPP technical standards is to be merely considered as an implementationexample, where many details are of less importance to the presentdisclosure.

Nevertheless, for the present disclosure it is assumed that the basicconcept behind the two-stage grant procedure will remain the same asdiscussed above. In particular, the basic concept will be explained inconnection with FIG. 7, which illustrates the functioning of a two-stagegrant including the transmission and reception of DCIs including triggerA and trigger B messages. For the following exemplary discussion it isassumed that the illustrated subframes are numbered by taking thesubframe at which the trigger B (i.e., the second stage uplinkscheduling message) is received in the UE, as reference subframe n; thepreceding and subsequent subframes are numbered accordingly. It isfurther assumed that the trigger A message is received at subframe n−3,and that a time window of length v is defined within which the two-stagegrant procedure can be validly performed. Put differently, the timewindow can be seen as defining the time period during which a trigger Bmessage can be received so as to actually trigger a corresponding uplinktransmission, based on the transmission parameters indicated by thetrigger A and/or trigger B messages.

The time window length v can exemplarily be indicated within the triggerA message, as exemplified above by the last 2 bits of the timing offsetfield of the DCI Formats 0A, 0B, 4A, 4B in TS 36.212 and Table 8.2.f ofTS 36.213.

When the trigger B message is received at subframe n, the UE willdetermine whether a related trigger A message was received by the UEwithin the time window of length v (starting immediately before thereception of the trigger B message, i.e., ranging from n−1 to n-v). Inthe illustrated scenario, the trigger A scheduling message was receivedin subframe n−3 and thus within the time window, thereby triggering theuplink transmission in the UE. The uplink transmission (i.e., PUSCH) isthen performed with a particular transmission timing offset at subframen+offset. The UE may perform the uplink transmission according to theinformation received in the trigger A message and trigger B message,e.g., using the indicated radio resources and modulation and codingscheme etc.

The exact PUSCH timing offset is of less importance to the presentdisclosure. Exemplarily, as currently standardized in TS 36.213, thePUSCH timing offset is “l+k+i”, where the parameter 1 is defined by thetrigger B message (see “Uplink transmission duration and offsetindication” field of DCI Format 1C in TS 36.212 and Table 13A-2 of TS36.213), where the parameter k is defined by the trigger a message (seethe first 2 bits of the “Timing offset” field of any of the DCI Formats0A, 0B, 4A, and 4B in TS 36.212, as well as Table 8.2e in TS 36.213).Parameter i is applicable in case that multiple uplink subframes arescheduled by a two-stage uplink scheduling procedure, and in that caseis running from 0 to the number of granted subframes minus 1 (otherwiseit is just 0). More details can be derived from the above cited section8 of TS 36.213. However, the PUSCH timing offset for performing theuplink transmission according to this two-stage uplink schedulingprocedure may also be defined differently or may be even predetermined.

As mentioned above, 3GPP has defined a two-stage scheduling procedurefor uplink transmissions in unlicensed cells. This two-stage schedulingprocedure however can be further improved.

BRIEF SUMMARY

Non-limiting and exemplary embodiments provide improved methods, userequipments, and radio base stations involved in scheduling uplinktransmissions to be performed by the user equipments in unlicensedcells. The independent claims provide non-limiting and exemplaryembodiments. Advantageous embodiments are subject to the dependentclaims.

According to several implementations of the aspects described herein,the scheduling of uplink transmissions via unlicensed cells is improved.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a user equipment for being scheduled with uplink radioresources. At least one unlicensed cell is configured for communicationbetween the user equipment and a radio base station that is responsiblefor scheduling uplink radio resources on the unlicensed cell. A receiverof the UE receives from the radio base station a first-stage uplinkresource scheduling message, indicating uplink radio resources usable bythe user equipment to perform an uplink transmission via the unlicensedcell. A processor of the UE determines whether the first-stage uplinkresource scheduling message is valid or not, which comprises determiningthat the first-stage uplink resource scheduling message is valid in caseone or more bits of one or more data fields in the first-stage uplinkresource scheduling message are set to respectively predeterminedvalues. The receiver receives from the radio base station a second-stageuplink resource scheduling message which is related to the first-stageuplink resource scheduling message. The processor determines, whenreceiving the second-stage uplink resource scheduling message, that anuplink transmission is scheduled in case the processor determined thatthe first-stage uplink resource scheduling message is valid. Atransmitter of the UE performs, in case it determined that an uplinktransmission is scheduled, an uplink transmission via the unlicensedcell according to the uplink radio resources indicated in thefirst-stage uplink resource scheduling message.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a radio base station for scheduling a user equipment withuplink radio resources on an unlicensed cell. At least one unlicensedcell is configured for communication between the user equipment and theradio base station. A processor of the radio base station generates afirst-stage uplink resource scheduling message, indicating uplink radioresources usable by the user equipment to perform an uplink transmissionvia the unlicensed cell. The generating comprises setting one or morebits of one or more data fields in the first-stage uplink resourcescheduling message to respectively predetermined values. That way, theuser equipment is able to determine that the first-stage uplink resourcescheduling message is valid in case the one or more bits of the one ormore data fields are confirmed to be set to the respective predeterminedvalues. A transmitter of the radio base station transmits thefirst-stage uplink resource scheduling message to the user equipment.The processor generates a second-stage uplink resource schedulingmessage related to the first-stage uplink resource scheduling message.The transmitter transmits the second-stage uplink resource schedulingmessage to the user equipment.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a method for operating a user equipment for being scheduledwith uplink radio resources. At least one unlicensed cell is configuredfor communication between the user equipment and a radio base stationthat is responsible for scheduling uplink radio resources on theunlicensed cell. The method comprises the following steps performed bythe user equipment. The UE receives from the radio base station afirst-stage uplink resource scheduling message, indicating uplink radioresources usable by the user equipment to perform an uplink transmissionvia the unlicensed cell. The UE determines whether the first-stageuplink resource scheduling message is valid or not, which comprisesdetermining that the first-stage uplink resource scheduling message isvalid in case one or more bits of one or more data fields in thefirst-stage uplink resource scheduling message are set to respectivelypredetermined values. The UE receives from the radio base station asecond-stage uplink resource scheduling message which is related to thefirst-stage uplink resource scheduling message. The UE determines, whenreceiving the second-stage uplink resource scheduling message, that anuplink transmission is scheduled in case the processor determined thatthe first-stage uplink resource scheduling message is valid. The UEperforms, in case it is determined that an uplink transmission isscheduled, an uplink transmission via the unlicensed cell according tothe uplink radio resources indicated in the first-stage uplink resourcescheduling message.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a method for operating a radio base station for schedulinga user equipment with uplink radio resources on an unlicensed cell. Atleast one unlicensed cell is configured for communication between theuser equipment and the radio base station. The method comprises thefollowing steps performed by the radio base station. The rear basestation generates a first-stage uplink resource scheduling message,indicating uplink radio resources usable by the user equipment toperform an uplink transmission via the unlicensed cell. The generatingcomprises setting one or more bits of one or more data fields in thefirst-stage uplink resource scheduling message to respectivelypredetermined values, for allowing the user equipment to determine thatthe first-stage uplink resource scheduling message is valid in case theone or more bits of the one or more data fields are confirmed to be setto the respective predetermined values. The radio base station transmitsthe first-stage uplink resource scheduling message to the userequipment. The radio base station generates a second-stage uplinkresource scheduling message related to the first-stage uplink resourcescheduling message. The radio base station transmits the second-stageuplink resource scheduling message to the user equipment.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and figures. The benefits and/oradvantages may be individually provided by the various embodiments andfeatures of the specification and drawings disclosure, and need not allbe provided in order to obtain one or more of the same.

These general and specific aspects may be implemented using a system, amethod, and a computer program, and any combination of systems, methods,and computer programs.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following exemplary embodiments are described in more detail withreference to the attached figures and drawings.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary downlink resource grid of a downlink slot of asubframe as defined for 3GPP LTE (Release 8/9),

FIG. 3 shows an exemplary uplink resource grid of an uplink slot of asubframe as defined for 3GPP LTE,

FIG. 4 illustrates an exemplary LAA scenario with several licensed andunlicensed cells,

FIG. 5 illustrates the transmission behavior for an LAA transmission,

FIG. 6 illustrates the timing between a Wi-Fi transmission and LAA UEdownlink burst for an unlicensed cell,

FIG. 7 exemplarily illustrates the two-stage uplink scheduling procedureas provided for uplink transmissions via unlicensed cells,

FIG. 8 is an exemplary and simplified flow diagram illustrating the UEbehavior according to an embodiment,

FIG. 9 is an exemplary and simplified flow diagram illustrating theeNodeB behavior according to an embodiment,

FIG. 10 is an exemplary and simplified flow diagram illustrating the UEbehavior according to another embodiment, and

FIG. 11 is an exemplary and simplified flow diagram illustrating the UEbehavior according to still another embodiment.

DETAILED DESCRIPTION

A mobile station or mobile node or user terminal or user equipment is aphysical entity within a communication network. One node may haveseveral functional entities. A functional entity refers to a software orhardware module that implements and/or offers a predetermined set offunctions to other functional entities of a node or the network. Nodesmay have one or more interfaces that attach the node to a communicationfacility or medium over which nodes can communicate. Similarly, anetwork entity may have a logical interface attaching the functionalentity to a communication facility or medium over which it maycommunicate with other functional entities or correspondent nodes.

The term “radio resources” as used in the set of claims and in theapplication is to be broadly understood as referring to physical radioresources, such as time-frequency resources.

The term “unlicensed cell” or alternatively “unlicensed carrier” as usedin the set of claims and in the application is to be understood broadlyas a cell/carrier operated in an unlicensed frequency band, with aparticular frequency bandwidth. Correspondingly, the term “licensedcell” or alternatively “licensed carrier” as used in the set of claimsand in the application is to be understood broadly as a cell/carrieroperated in a licensed frequency band, with a particular frequencybandwidth. Exemplarily, these terms are to be understood in the contextof 3GPP as of Release 12/13 and the Licensed-Assisted Access Work Item.

The term “first-stage uplink resource scheduling message” as used in theset of claims and in the application is to be understood broadly as amessage corresponding to the first stage of a multi-stage (in this casetwo-stage) uplink scheduling procedure. The term “trigger A message” isused interchangeably as well. Correspondingly, the term “second-stageuplink resource scheduling message” as used in the set of claims and inthe application is to be understood broadly as a message correspondingto the second stage of the multi-stage (in this case two-stage) uplinkscheduling procedure. The term “trigger B message” is usedinterchangeably as well. Alternatively, the terms “first-stage message”and “second-stage message” of the uplink resource scheduling can be usedrespectively to denote the trigger A and trigger B messages.

As explained in the background section, 3GPP is currently in the processof enhancing the licensed-assisted access (LAA) also for the uplink andhas foreseen a two-stage uplink resource allocation procedure in whichtwo separate uplink resource allocation messages are transmitted by theeNB to trigger one uplink transmission (briefly denoted e.g., Trigger Aand Trigger B as introduced in the background section). The two-stageuplink scheduling procedure (as exemplarily illustrated in FIG. 7) isnot optimal as will be explained in the following.

When the eNB transmits a Trigger B message, any UE that received aTrigger A message up to v subframes earlier will be scheduled to performan uplink transmission. In particular, while the trigger A message isUE-specific, the trigger B message is not. Thus, even if the trigger Bmessage is transmitted for the purpose of scheduling an uplinktransmission in connection with a specific previously-transmittedtrigger A message (or a plurality thereof addressed to different UEs),other UEs that also receive this trigger B message may wrongly considerthat the trigger B message is related to a previously received trigger Amessage.

This problem is also present in the case that a UE has falsely detecteda trigger A message. In particular, a UE, when receiving a DCI messageof Format 0A, 0B, 4A, 4B that shall not be a Trigger A message, maywrongly determine the content of the “PUSCH trigger A” field (“1”instead of “0”) (e.g., due to transmission errors), thereby concludingerroneously that it received a trigger A message. It will then, whenreceiving a trigger B message (possibly intended for another UE),perform an uplink transmission (provided the trigger A message wasreceived in the time window of length v before reception of the triggerB message; see also FIG. 7). A falsely detected trigger A message isparticularly problematic if it causes a multi-subframe transmission, assupported by DCI messages of Formats 0B and 4B.

These erroneous uplink transmissions by the UE (be they single subframeor multi subframe) were not intended by the eNodeB which thus can leadto intracell and intercell interference with transmissions of other UEs.It may also affect the coexistence with other unlicensed technologies(e.g., WiFi).

In addition, any corresponding UL-SCH Transport Blocks transmitted as aresult from such an unintended transmissions are not expected by theeNodeB, and consequently, the eNodeB may never receive those UL-SCHTransport Blocks. To resolve this, a higher-layer retransmissionprotocol is needed to convey the corresponding data after thelower-layer retransmission protocols have unsuccessfully timed out,causing extra delay and potentially channel occupancy time.

The following exemplary embodiments are conceived by the inventor tomitigate one or more of the problems explained above.

Particular implementations of the various embodiments are to beimplemented in the wide specification as given by the 3GPP standards andexplained partly in the background section, with the particular keyfeatures being added as explained in the following embodiments. Itshould be noted that the embodiments may be advantageously used forexample in a mobile communication system, such as 3GPP LTE-A (Release10/11/12/13/14 and later releases) communication systems as described inthe Technical Background section above, but the embodiments are notlimited to its use in these particular exemplary communication networks.

The explanations should not be understood as limiting the scope of thedisclosure, but as a mere example of embodiments to better understandthe present disclosure. A skilled person is aware that the generalprinciples of the present disclosure as generally outlined in the set ofclaims and in the explanations given in the description can be appliedto different scenarios and in ways that are not explicitly described inthe following. For illustration and explanation purposes, severalassumptions are made which however shall not unduly restrict the scopeof the following embodiments.

The various embodiments mainly provide an improved uplink schedulingprocedure for unlicensed cells, particularly when using two-stageresource allocations. Other functionality (i.e., functionality notchanged by the various embodiments) may remain exactly the same asexplained in the background section or may be changed without anyconsequences to the various embodiments, for instance functions andprocedures defining how the uplink transmission is actually performed(e.g., segmentation, modulation, coding, beamforming, multiplexing) orfunctions and procedures that allow the UE to transmit in unlicensedcells in the first place (e.g., RRC configuration, LBT, CCA etc.).

In the following, an embodiment for solving the above problem(s) will bedescribed in detail, which will be explained by using the followingexemplary scenario, devised to easily explain the principles of theembodiment. The principles however can also be applied to otherscenarios, some of which will be explicitly mentioned in the following.

As explained in the background section, 3GPP has enhanced currentsystems by introducing LAA, licensed-assisted access, as well as eLAAfor uplink transmissions using unlicensed cells being operated onchannel(s) in the unlicensed frequency spectrum. In the following, ascenario is assumed where the UE is configured with at least oneunlicensed cell and optionally with at least one further licensed cell.Several UEs may be communicating with the eNB via the unlicensed cell.Although the following explanations are based on such a scenario, thedifferent embodiments also apply to scenarios where the unlicensed cellis operated in a standalone manner (i.e., without being assisted by acorresponding licensed cell). The unlicensed cell can be configuredbetween the eNodeB and the UE in the usual manner as described in thebackground section. Accordingly, the unlicensed cell is operated on aparticular channel in the unlicensed frequency spectrum.

It is further assumed that uplink transmissions, to be performed by UEsvia unlicensed cells, are scheduled by the eNB in a suitable manner,which also includes the use of two-stage grants as explained in thebackground section and in the context of the problems that areidentified for two-stage grants The following embodiments shall improvethe two-stage uplink scheduling procedure such that the false-detectionrisk for the first message (i.e., trigger A) is reduced, so as to avoidunwanted uplink transmissions from UEs after receiving the secondmessage (i.e., trigger B message) of the two-stage uplink schedulingprocedure.

The gist of the embodiments revolves around the idea of using one ormore bits of one or more data fields of the trigger A message to allowthe UE to additionally verify that the received message is indeed atrigger A message. Correspondingly, the eNodeB, when generating thetrigger A message, sets these one or more bits of the one or more datafields (exemplarily termed in the following “verification data fields”;alternatively “validation data fields”) to respectively predeterminedvalues. Other data fields of the trigger A message may be set by theeNodeB in accordance with the uplink resource scheduling procedureperformed in the usual manner. For instance, exemplarily assuming thatthe trigger A message (and not the trigger B message) shall convey suchinformation, the trigger A message may further indicate suitable uplinkresources that are usable by the UE to perform an uplink transmissionvia the unlicensed cell; and/or a corresponding HARQ process may beindicated; and/or a suitable modulation and coding scheme can beinstructed; and/or cross carrier scheduling can be performed by settingthe suitable carrier indicator bits; etc. The trigger A message is thentransmitted from the eNodeB to the UE.

The UE then, upon receiving the trigger A message, uses the content ofthe one or more verification data fields to verify whether the receivedtrigger A message is indeed a valid trigger A message or not.Correspondingly, the UE determines whether the verification data fieldsare set to the respectively predetermined values or not. In case thebit(s) of the verification data field(s) coincide with the predeterminedvalues, the UE considers the received trigger A message to be valid, andconversely, in case the bit(s) of the verification data field(s) do notcoincide with the predetermined values, the UE considers the receivedtrigger A message to be invalid. Only a trigger A message that was notconsidered invalid can—together with the corresponding trigger B messagereceived in a timely manner afterwards—schedule an uplink transmission.

The scenario of FIG. 7 can be reused to explain the embodiments. Afterthe eNodeB has transmitted the trigger A message at subframe n−3 withthe bits(s) of the verification data field(s) set accordingly, it maytransmit the corresponding trigger B message three subframes later, atsubframe n. For instance, the eNB may detect that the channel of theunlicensed cell is free to use, and will then determine to finallyschedule the UE by transmitting a suitable trigger B message at subframen.

The UE will receive the trigger B message accordingly, and then shalldetermine whether an uplink transmission is indeed intended to bescheduled by the eNB. As explained above, one requirement forsuccessfully triggering an uplink transmission in the UE is that the UEverifies the previously received trigger A message to be indeed atrigger A message using the verification data field(s) as generallyexplained above. Consequently, the UE determines that the uplinktransmission is indeed scheduled, in case at least the trigger A messagewas verified to be valid (and the trigger A message is not invalidatedfor another reason). As a result, the UE will prepare and perform theuplink transmission in accordance with any transmission parametersindicated in the trigger A message and/or trigger B message; e.g., usingthe radio resources on the unlicensed cell as indicated.

FIG. 8 is a flow diagram illustrating exemplarily the UE behavior andthe main steps to be performed by the UE so as to allow the schedulingof uplink radio resources to the UE for performing an uplinktransmission via an unlicensed cell using the improved two-stage uplinkscheduling procedure according to the embodiment(s) explained above. Asapparent from FIG. 8, the UE shall receive both the trigger A message(i.e., termed first-stage message of uplink resource allocation in thefigure) and the trigger B message (i.e., termed second-stage message ofuplink resource allocation in the figure). According to the exemplaryembodiment in FIG. 8, the verification/validation of the trigger Amessage is performed after receiving the trigger B message, bydetermining whether the verification data field(s) are set topredetermined values or not. In the affirmative case (“Yes” in figure),the trigger A message is considered valid, and the UE may proceed toperform the uplink transmission. In the negative case (“No” in figure),the trigger A message is considered invalid, and the UE shall notperform the uplink transmission but may await further trigger A and/ortrigger B messages.

FIG. 9 is a flow diagram illustrating exemplarily the eNB behavior andthe main steps to be performed by the eNB as to schedule uplink radioresources to the UE for performing an uplink transmission via anunlicensed cell using the improved two-stage uplink scheduling procedureaccording to the embodiment(s) explained above. As apparent from FIG. 9,the eNB can prepare the trigger A message (i.e., termed first-stagemessage of uplink resource allocation) for the UE, which includes thesetting of the one or more bits of the one or more particular datafields to predetermined values so as to allow the verifying of thetrigger A message at the UE. The trigger A message is then transmittedto the UE. Afterwards, the eNB—when deciding to finally schedule theuplink transmission for the UE—prepares and transmits the trigger Bmessage (i.e., termed second-stage message of uplink resource allocationin the figure) to the UE. If the UE behaves accordingly and performs theuplink transmission, e.g., to the eNB, the eNB may receive the uplinktransmission, scheduled before, from the UE (not illustrated).

By providing additional verification data bits to verify the trigger Amessage, the false detection rate (risk) is reduced. The amount of falsedetection reduction depends on the number of bits that are used for theverification. The more bits are used for the verification, the more thefalse-detection of a trigger A message is reduced. In particular, oneverification bit (either with the predetermined value 0 or 1) halves therisk etc. Consequently, the amount of bits that shall be foreseen forimproving the detection of the trigger A message in the UE depends onthe level of reliability that shall be achieved. Moreover, as willbecome apparent from later discussion, there is a tradeoff between theimproved trigger A message detection and the loss of those verificationbits that can/could be used for other purposes.

In the above, a general embodiment and its advantages has beenexplained. In the following, variations of this general embodiment willbe explained, e.g., providing more detailed implementations, providingan exemplary implementation in existing 3GPP communication systems, orproviding further advantages.

Advantageous embodiments differ with regard to which and how many bitsof which data fields are to be used for the verification. In general,one or more specific bits belonging to one or more specific data fieldswithin the trigger A message can be used in said respect, taking intoaccount that the eNB as well as the UEs should know in advance which areexactly used. Depending on the actual implementation, for example aspecific data field having one or more bits can foresee in a trigger Amessage, which is then set by the eNB accordingly and which content isthen checked by the UE to additionally verify the trigger A message.

In an exemplary implementation in the 3GPP communication system asexplained in the background section, the trigger A message is a messageaccording to one of the DCI Formats 0A, 0B, 4A, 4B. As apparent from thebackground section, and particularly from the corresponding 3GPPtechnical standard TS 36.212, each of these DCI formats defines datafields usable for specific purposes. Put briefly, according toadvantageous embodiments, one or more of these data fields are reused toconvey the verification bits, as will be explained in the following.

A suitable data field to be used for trigger A message verification isthe CSI request data field, which is 1, 2, or 3 bits and can be used tocontrol aperiodic reporting of channel state information using PUCSH.Details on how the CSI request data field shall be usually employed bythe eNB and UE is apparent from section 7.2.1 of TS 36.213 v14.0.0,incorporated herein by reference. In brief, whether the CSI request datafield includes 1, 2, or 3 bits depends on different configuration orsystem parameters. For example, the 3-bit field applies to UEs that areconfigured with more than five DL cells and when the corresponding DCIformat is mapped onto the UE specific search space given by the C-RNTIas defined in 3GPP TS 36.213. The 2-bit field applies to UEs configuredwith no more than five DL cells and to

-   -   UEs that are configured with more than one DL cell and when the        corresponding DCI format is mapped onto the UE specific search        space given by the C-RNTI as defined in 3GPP TS 36.213;    -   UEs that are configured by higher layers with more than one CSI        process and when the corresponding DCI format is mapped onto the        UE specific search space given by the C-RNTI as defined in 3GPP        TS 36.213;    -   UEs that are configured with two CSI measurement sets by higher        layers with the parameter csi-MeasSubframeSet, and when the        corresponding DCI format is mapped onto the UE specific search        space given by the C-RNTI as defined in 3GPP TS 36.213. The        1-bit field applies otherwise.

One or more bits of the CSI request field of any DCI Format 0A, 0B, 4A,or 4B can be used according to the embodiments to implement theadditional trigger A message verification. It may not be advantageous toonly use less than all available bits of the CSI request field.Especially for the CSI request in an LTE system using triggeredscheduling, the subframe containing the CSI report is only fully knownafter the reception of the trigger B message. However, the timereference for the CSI report is defined as a function of thetransmission time of the CSI report, i.e., of the subframe conveying theCSI report. Since the calculation of a CSI report is quite complex, itis a rather demanding task on the signal processing capabilities,especially if the time between the reception of the trigger B messageand the intended CSI reporting subframe is less than 4 subframes. Toavoid these issues for the UE implementation, it is more feasible if theUE can always assume that a triggered scheduling procedure will neverrequest a CSI report. Consequently, in one advantageous implementation,all bits that are available in the CSI request field are used for thetrigger A message verification.

Alternatively or additionally, a suitable data field to be used fortrigger A message verification is the SRS request data field, which is 1or 2 bits long depending on the actual DCI Format, and which is used inconnection with the UE sounding procedure so as to allow the eNB torequest the UE to transmit a sounding reference signal, as e.g.,currently defined in section 8.2 of TS 36.213 v14.0.0 incorporatedherein by reference. The one or two bits can be used according to theembodiments to implement the additional verification. It may not beadvantageous to only use less than all available bits of the SRS requestdata field considering that any SRS transmitted by a UE in a subframemay prohibit the successful reception of PUSCH data from other UEs andSRS from the triggered UE at least on those resources that are occupiedby SRS due to the mutually generated interference Consequently, in oneadvantageous implementation, all bits that are available in the SRSrequest field are used for the trigger A message verification, and SRStriggering in a triggered scheduling procedure is effectively disabled.However, if the scheduler can avoid the interference by accepting thecorresponding restrictions on the scheduling flexibility, it is possiblefor the system to keep a limited SRS triggering flexibility togetherwith an improved trigger A message verification by using less than allavailable bits of the SRS request data field for the verification. Thecorresponding limited SRS triggering capability preferably represents atleast the state that no SRS is triggered, and SRS configurabilityoption(s) that is/are available if no SRS request data fields are usedfor trigger A message verification.

Alternatively or additionally, a suitable data field to be used fortrigger A message verification is the TPC command data field, which is 2bits long, and is used by the eNodeB to control uplink power used in theUE to perform uplink transmissions, as e.g., currently defined insection 5.1.1.1 of TS 36.213 v 14.0.0, incorporated herein by reference.One or 2 bits of the TPC command data field can be used according to theembodiments to implement the additional trigger A message verification.When using only one of the 2 bits of the TPC command field for thetrigger A message verification, the remaining one bit can be still usedto convey transmit power commands as initially intended by said field.As a result of reducing the TPC command field to only one bit, only twodifferent TPC commands can be instructed to the UE, for instance+1 and−1 dB or any other suitable values.

Alternatively or additionally, a suitable data field to be used fortrigger A message verification is the Timing Offset field, used in thecontext of the two-stage uplink scheduling procedure as previouslydefined in the background section. Particularly, the timing offset fieldis 4 bits long, wherein, in case of triggered scheduling, the first twobits of the timing offset field normally indicate the relative timingoffset for the PUSCH transmission, while the last two bits normallyindicate the time window within which the scheduling of PUSCH viatriggered scheduling is valid. One or more bits of the timing offsetfield can be used according to the embodiments to implement theadditional trigger A message verification. According to an advantageouslimitation thereof, only one bit of the first two bits of the timingoffset field shall be reused for the trigger A message verification,such that the remaining bit could still be used to indicate a relativetiming offset for the PUSCH transmission as initially intended by saidfield. As a result of reducing the timing offset field to only one bit,only two different timing offset values can be instructed, for instanceany value from the values currently specified in Table 8.2e in thecurrent 3GPP specification TS 36.213 section 8; the relative timingoffset “k” with 2 bits can take the values 0, 1, 2, or 3. As explainedbefore in detail, the PUSCH transmission is performed after receivingthe trigger B message including a particular timing offset whichaccording to the current specification in section 8 of 3GPP TS 36.213,amounts to “l+k+i” subframes. When disregarding for the moment the valueof the parameter i which is not dependent on the actual two-stage grantprocedure, the timing offset is configured to by using the twoparameters 1 and k. The parameter 1 as part of the trigger B message candistinguish between the values 1, 2, 3, 4, and 6. In order to stillcover the smallest and largest total delay (l+k), the reduced field forindicating the relative timing offset, having one bit only, shalladvantageously distinguish between the values k=0 and k=3. In that case,the total delay can be {1; 2; 3; 4; 5; 6; 7; 9}.

Additionally, or alternatively, instead of having a fixed association,the actual timing offset value [0, 1, 2, or 3] that is associated witheach bit value [0 or 1] of the reduced timing offset field can beconfigured, e.g., by the eNodeB, for instance using higher layersignaling such as RRC.

Messages according to the DCI Formats 0A, 0B, 4A, 4B include furtherfields that could theoretically be reused for the purpose of theadditional verification. However, the data fields mentioned above arethe most advantageous ones.

One possible drawback of reusing data fields initially intended forother purposes (see above CSI requesting, SRS request, TCP command) isthat this field cannot be used anymore as initially intended (when beingused for a trigger A message verification). However, this drawback isnot as severe in view of that the eNodeB is able to convey the necessaryinformation (be it CSI request, SRS request, TPC command etc.) inanother way, e.g., Within another DCI message. For instance, even if etrigger A messages of the two-stage uplink resource allocation do nolonger allow to request a CSI/SRS, the eNodeB can request the CSI/SRS byusing one-stage uplink resource allocation messages e.g., for thelicensed or unlicensed cell. The same basically applies to the reusingof the TPC field. As a result, the overall functionality available tothe eNodeB is not lost for the system. Rather, the eNodeB may simply useother messages to convey the corresponding requests and commands.

Moreover, the embodiments can also vary as to the time at which theverification of the trigger A message is performed. In particular, thedetermination of whether the first stage uplink scheduling message isvalid or not based on the particular verification data field(s), can beperformed at any suitable time. Although in the description so far andparticularly in FIG. 8 the verification of the trigger A message isdescribed as being performed immediately upon receiving the trigger Bmessage, the verification procedure can also be performed at anothertime as long as it is done in a timely manner to decide on whether thetwo-stage-triggered uplink transmission is to be performed or not. Forinstance, the verification can be performed when receiving the trigger Amessage or at any time after having received the trigger A message butbefore receiving the trigger B message. The approaches are functionallyequivalent; performing the verification upon the trigger A messagereception is beneficial in that after the reception of a trigger Bmessage, no trigger A verification steps are necessary that may delaythe response to the trigger B, however it implies processing theverification steps even if no trigger B command is received in thesubsequent subframe. Performing the verification upon the trigger Bmessage reception has the advantage of processing the verification stepsonly if the PUSCH transmission is detected to be triggered by a secondstage DCI, but requires processing steps for verification before thePUSCH transmission itself can be processed.

Although not specifically mentioned before, the two-stage uplinkresource scheduling procedure as explained so far may optionally alsoimplement a time window during which the two-stage triggered schedulinghas to occur. In particular, a time window of length v is given (e.g.,as indicated by the trigger A message, e.g., in the last two bits of itstiming offset field; see TS 36.212), during which both the trigger A andtrigger B messages of the two-stage uplink resource scheduling procedurehave to be received. Correspondingly, as exemplarily implemented in the3GPP standards, the UE, upon receiving the trigger B message, determineswhether it was received within the indicated time window after receivinga corresponding trigger A message (or put the other way around, whethera corresponding trigger A message was received within a time windowbefore the UE received the trigger B message). In case the trigger Bmessage was received too late (i.e., a corresponding trigger A messagewas not received within the time window before having received thetrigger B message), the two-stage scheduling is not valid and acorresponding uplink transmission is not performed by the UE. This UEbehavior is illustrated in the exemplary and simplified flow diagram ofFIG. 10.

As mentioned before, the trigger A message is usually addressed to aspecific UE, which can be done in the usual manner by masking the CRC ofthe DCI message with a UE-specific identity, such as the C-RNTI. Thetrigger B message on the other hand is not UE-specific, but commonlyaddressed to a plurality of UEs; which also can be done in the usualmanner by masking the CRC of the DCI message (Format 1C) with a commonRNTI (such as the CC-RNTI).

Data integrity of any DCI message (including the trigger A and Bmessages) is usually verified using the cyclic redundancy check, CRC,bits in the DCI messages. This CRC verification is performed in additionto the trigger A message verification as explained above in connectionwith the embodiments. Only if both the CRC verification as well theverification of data field contents (see FIG. 8) are successful, thetrigger A message is confirmed to be valid and the UE may proceed toperform the uplink transmission accordingly. This UE behavior isillustrated in the exemplary and simplified flow diagram of FIG. 11. Theorder of the steps for CRC verification and trigger A messageverification can also be reversed.

The UE as well as the eNodeB need to know about the verification datafields and the corresponding predetermined values so as to allow theabove improved two-stage grant procedure to function properly. This canbe achieved in different manners. For instance, the particular bitsand/or the particular data fields can be fixed in a correspondingtechnical standard (e.g., in TS 36.213) and thus available to the UE aspart of its software/firmware. For example, the following exemplarytable can be provided in the standard:

Special fields for triggered scheduling PDCCH/EPDCCH Validation

DCI Format 0A DCI Format 0B/4A/4B CSI request all bits set to ‘0’ allbits set to ‘0’ SRS request set to ‘0’ set to ‘00’

Alternatively, instead of fixing the one or more verification datafield(s) and corresponding one or more bit(s), these can be in part orfully configurable by the eNB, for example by using higher layersignaling such as RRC signaling.

According to one specific implementation, the embodiment may beimplemented in a 3GPP communication system as currently standardized.

Correspondingly, the standard TS 36.213 could be exemplarychanged/extended as follows:

“A UE shall validate an assignment by PDCCH/EPDCCH if DCI Format0A/0B/4A/4B is detected where all of the following conditions are met:

-   -   the CRC parity bits obtained for the PDCCH/EPDCCH payload are        scrambled with the C-RNTI    -   the PUSCH trigger A bit is set to ‘1’.        Validation is achieved if all the fields for the respective used        DCI are set according to Table A-1.        If validation is achieved, the UE shall consider the received        DCI information accordingly as valid.        If validation is not achieved, the received DCI shall be        considered by the UE as having been received with a non-matching        CRC.”

TABLE A-1 Special fields for triggered scheduling PDCCH/EPDCCHValidation DCI Format 0A DCI Format 0B/4A/4B CSI request all bits set to‘0’ all bits set to ‘0’ SRS request set to ‘0’ set to ‘00’

In the above exemplary implementation all bits of the CSI request datafield and the SRS request data field are used as the verification datafields as explained above.

Hardware and Software Implementation of the Present Disclosure

Other exemplary embodiments relate to the implementation of the abovedescribed various embodiments using hardware, software, or software incooperation with hardware. In this connection a user terminal (mobileterminal) and an eNodeB (base station) are provided. The user terminaland base station is adapted to perform the methods described herein,including corresponding entities to participate appropriately in themethods, such as receiver, transmitter, processors.

It is further recognized that the various embodiments may be implementedor performed using computing devices (processors). A computing device orprocessor may for example be general purpose processors, digital signalprocessors (DSP), application specific integrated circuits (ASIC), fieldprogrammable gate arrays (FPGA) or other programmable logic devices,etc. The various embodiments may also be performed or embodied by acombination of these devices. In particular, each functional block usedin the description of each embodiment described above can be realized byan LSI as an integrated circuit. They may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. They may include a data input and output coupledthereto. The LSI here may be referred to as an IC, a system LSI, a superLSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit or a general-purpose processor. In addition, a FPGA(Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuits cells disposed inside the LSIcan be reconfigured may be used.

Further, the various embodiments may also be implemented by means ofsoftware modules, which are executed by a processor or directly inhardware. Also a combination of software modules and a hardwareimplementation may be possible. The software modules may be stored onany kind of computer readable storage media, for example RAM, EPROM,EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. It shouldbe further noted that the individual features of the differentembodiments may individually or in arbitrary combination be subjectmatter to another embodiment.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments. The present embodiments are,therefore, to be considered in all respects to be illustrative and notrestrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A user equipment for being scheduled withuplink radio resources, wherein at least one unlicensed cell isconfigured for communication between the user equipment and a radio basestation that is responsible for scheduling uplink radio resources on theunlicensed cell, the user equipment comprising: a receiver, which inoperation, receives, from the radio base station, a first-stage uplinkresource scheduling message and a second-stage uplink resourcescheduling message that is related to the first-stage uplink resourcescheduling message, the first-stage uplink resource scheduling messageindicating uplink radio resources usable by the user equipment toperform an uplink transmission via the unlicensed cell and a timeperiod, the second-stage uplink resource scheduling message beingreceived subsequent to the first-stage uplink resource schedulingmessage being received, a processor, which in operation, determineswhether the first-stage uplink resource scheduling message is valid ornot, the processor, in operation, determines the first-stage uplinkresource scheduling message is valid in case one or more bits of one ormore data fields in the first-stage uplink resource scheduling messageare set to respectively predetermined values and the second-stage uplinkresource scheduling message is received within the time period afterreception of the first-stage uplink resource scheduling message, theprocessor, in operation, determines that the uplink transmission isscheduled in case the processor determined that the first-stage uplinkresource scheduling message is valid; and a transmitter, which inoperation and in case the processor determined that the uplinktransmission is scheduled, performs the uplink transmission via theunlicensed cell according to the uplink radio resources indicated in thefirst-stage uplink resource scheduling message.
 2. The user equipmentaccording to claim 1, wherein the predetermined values of the one ormore bits of the one or more data fields are fixed in the user equipmentand the radio base station or are configured by the radio base stationin the user equipment using higher-layer signaling.
 3. The userequipment according to claim 1, wherein the one or more data fields inthe first-stage uplink resource scheduling message are one of thefollowing fields regularly defined for a resource scheduling message: aChannel State Information, CSI, request data field, requestingtransmission of a channel state information message from the userequipment, or a Sounding Reference Symbol, SRS, request data field,requesting transmission of a sounding reference symbol from the userequipment, or a transmit power command, TPC, data field, indicating achange in transmit power for the user equipment, or a timing offset datafield, indicating a timing offset for the user equipment to perform theuplink transmission, wherein one of two bits of the TPC data field isused for determining whether the first-stage uplink resource schedulingmessage is valid, and the other of the two bits of the TPC data field isused for indicating the change in the transmit power for the userequipment, wherein one of two bits of the timing offset data field isused for determining whether the first-stage uplink resource schedulingmessage is valid, and the other of the two bits of the timing offsetdata field is used for determining the timing offset for the userequipment to perform the uplink transmission, wherein values of thetiming offset associated with the other of the two bits of the timingoffset data field are the lowest and highest value associated with thetwo bits of the timing offset data field or are configurable by theradio base station via Radio Resource Control, RRC, signalingtransmitted to the user equipment.
 4. The user equipment according toclaim 1, wherein the first-stage uplink resource scheduling message isaddressed to the user equipment, and the second-stage uplink resourcescheduling message is commonly addressed to a plurality of userequipments, wherein the first-stage uplink resource scheduling messageis addressed to the user equipment by means of a user-equipment-specificidentity employed in the transmission of the first-stage uplink resourcescheduling message, and wherein the user-equipment-specific identity isconfigurable, and wherein the second-stage uplink resource schedulingmessage is commonly addressed to a plurality of user equipmentsreceiving the second-stage uplink resource scheduling message by meansof a shared identity employed in the transmission of the second-stageuplink resource scheduling message, wherein the shared identity ispre-defined and common to a plurality of user equipments.
 5. The userequipment according to claim 1, wherein the time period is a period inwhich the first-stage uplink resource scheduling message can beconsidered together with the second-stage uplink resource schedulingmessage.
 6. The user equipment according to claim 1, wherein thefirst-stage uplink resource scheduling message indicates a timing offsetfor the user equipment to perform the uplink transmission, and whereinthe second-stage uplink resource scheduling message indicates a furthertiming offset for the user equipment to perform the uplink transmission,wherein the transmitter, in operation, performs the uplink transmissionat least after a sum of the timing offset and the further timing offsetupon receiving the second-stage uplink resource scheduling message. 7.The user equipment according to claim 1, wherein the first-stage uplinkresource scheduling message is a downlink control information, DCI,message of format 0A, 0B, 4A, or 4B, respectively including afirst-stage flag indicating that the DCI message is a first message of atwo-stages uplink resource scheduling, wherein the second-stage uplinkresource scheduling message is a downlink control information, DCI,message of format 1C, including a second-stage flag indicating that theDCI message is a second message of a two-stages uplink resourcescheduling.
 8. A radio base station for scheduling a user equipment withuplink radio resources on an unlicensed cell, wherein at least oneunlicensed cell is configured for communication between the userequipment and the radio base station, the radio base station comprising;a processor, which in operation, generates a first-stage uplink resourcescheduling message and a second-stage uplink resource scheduling messagethat is related to the first-stage uplink resource scheduling message,the first-stage uplink resource scheduling message indicating uplinkradio resources usable by the user equipment to perform an uplinktransmission via the unlicensed cell and a time period, the generatingof the first-stage uplink resource scheduling message including settingone or more bits of one or more data fields in the first-stage uplinkresource scheduling message to respectively predetermined values, theuser equipment determines that the first-stage uplink resourcescheduling message is valid in case the one or more bits of the one ormore data fields are confirmed to be set to the respective predeterminedvalues and the second-stage uplink resource scheduling message isreceived within the time period after reception of the first-stageuplink resource scheduling message, the user equipment determines thatthe uplink transmission is scheduled in case the user equipmentdetermines that the first-stage uplink resource scheduling message isvalid, the user equipment, in case the user equipment determines thatthe uplink transmission is scheduled, performs the uplink transmissionvia the unlicensed cell according to the uplink radio resourcesindicated in the first-stage uplink resource scheduling message; and atransmitter, which in operation, transmits the first-stage uplinkresource scheduling message to the user equipment, and transmits thesecond-stage uplink resource scheduling message to the user equipmentsubsequent to the first-stage uplink resource scheduling message beingtransmitted to the user equipment.
 9. The radio base station accordingto claim 8, wherein the predetermined values of the one or more bits ofthe one or more data fields are fixed in the user equipment and theradio base station or are configured by the radio base station in theuser equipment, using higher-layer signaling.
 10. The radio base stationaccording to claim 8, wherein the one or more data fields in thefirst-stage uplink resource scheduling message are one of the followingfields regularly defined for a resource scheduling message: a ChannelState Information, CSI, request data field, requesting transmission of achannel state information message from the user equipment, or a SoundingReference Symbol, SRS, request data field, requesting transmission of asounding reference symbol from the user equipment, or a transmit powercommand, TPC, data field, indicating a change in transmit power for theuser equipment, or a timing offset data field, indicating a timingoffset for the user equipment to perform the uplink transmission,wherein one of two bits of the TPC data field is used for determiningwhether the first-stage uplink resource scheduling message is valid, andthe other of the two bits of the TPC data field is used for indicatingthe change in the transmit power for the user equipment, wherein one oftwo bits of the timing offset data field is used for determining whetherthe first-stage uplink resource scheduling message is valid, and theother of the two bits of the timing offset data field is used forindicating the timing offset for the user equipment to perform theuplink transmission, wherein values of the timing offset associated withthe other of the two bits of the timing offset data field are the lowestand highest value associated with the two bits of the timing offset datafield or are configurable by the radio base station, via Radio ResourceControl, RRC, signaling transmitted to the user equipment.
 11. The radiobase station according to claim 8, wherein the first-stage uplinkresource scheduling message is addressed to the user equipment, and thesecond-stage uplink resource scheduling message is commonly addressed toa plurality of user equipments.
 12. The radio base station according toclaim 8, wherein the time period is a period in which the first-stageuplink resource scheduling message can be considered together with thesecond-stage uplink resource scheduling message.
 13. The radio basestation according to claim 8, wherein the first-stage uplink resourcescheduling message indicates a timing offset for the user equipment toperform the uplink transmission, and wherein the second-stage uplinkresource scheduling message indicates a further timing offset for theuser equipment to perform the uplink transmission, such that the userequipment performs the uplink transmission at least after a sum of thetiming offset and the further timing offset upon receiving thesecond-stage uplink resource scheduling message, wherein the first-stageuplink resource scheduling message is a downlink control information,DCI, message of format 0A, 0B, 4A, or 4B, respectively including afirst-stage flag indicating that the DCI message is a first message of atwo-stages uplink resource scheduling, wherein the second-stage uplinkresource scheduling message is a downlink control information, DCI,message of format 1C, including a second-stage flag indicating that theDCI message is a second message of a two-stages uplink resourcescheduling.
 14. A method performed by a user equipment for beingscheduled with uplink radio resources, wherein at least one unlicensedcell is configured for communication between the user equipment and aradio base station that is responsible for scheduling uplink radioresources on the unlicensed cell, the method comprising: receiving, fromthe radio base station, a first-stage uplink resource scheduling messageindicating uplink radio resources usable by the user equipment toperform an uplink transmission via the unlicensed cell and a timeperiod; receiving, from the radio base station and subsequent to thefirst-stage uplink resource scheduling message being received, asecond-stage uplink resource scheduling message that is related to thefirst-stage uplink resource scheduling message; determining whether thefirst-stage uplink resource scheduling message is valid or not, thefirst-stage uplink resource scheduling message being determined to bevalid in case one or more bits of one or more data fields in thefirst-stage uplink resource scheduling message are set to respectivelypredetermined values and the second-stage uplink resource schedulingmessage is received within the time period after reception of thefirst-stage uplink resource scheduling message; determining that theuplink transmission is scheduled in case the first-stage uplink resourcescheduling message is determined to be valid; and performing, in case itis determined that the uplink transmission is scheduled, the uplinktransmission via the unlicensed cell according to the uplink radioresources indicated in the first-stage uplink resource schedulingmessage.